Acute stress and gut microbiome: a potential in vivo rodent model to study molecular and pathological mechanisms

studying molecular

changes in organ and body weights after HLU) [10]. The animals are freed from the string after the suspension to allow them to recover and determine acute stress reversal. Our preliminary findings suggest that various biomarkers associated with acute stress were observed in animals during stressful HLU, compared with animals kept under normal conditions, such as vasodilator-stimulated phosphoprotein, myeloperoxidase, high sensitivity C reactive protein, IL-8, plasminogen activator inhibitor-1, intercellular adhesion molecule-1 and monocyte chemoattractant protein-1. The use of the model can also help reveal epigenetic changes using transcriptomic analysis in the brain, gut, liver, muscles, lungs, heart and other tissues. In this regard, the aforementioned animal model is highly advantageous, in that, blood, sweat, cerebrospinal fluid (CSF), tissues, oral and gut microbiome samples can be collected to carryout molecular studies. Blood can be collected by cardiac puncture that allows up to 10 ml of blood from a single 150 g rat. The CSF is collected from cisterna magna of the rats. Briefly, rats are anesthetized and a butterfly needle connected to a syringe is directly punctured into the cisterna magna, and the noncontaminated sample is drawn into the syringe. The tubing is cut with a pair of scissors from the clear part to avoid blood contamination. Then the clear CSF (ca. 100-250 μl per rat) is obtained. For sweat induction and collection, three washes of distilled water are used to clean the footpads of anesthetized rats. The next step is to submerge the footpads in light mineral oil to stop evaporative losses. Next, pilocarpine (10 mg/kg) in water is injected subcutaneously dorsal to the scapula to induce sweating. Sweat is collected using a 20-70 nl constriction pipette, with mineral oil acting as a constant vapor barrier [12]. For epigenetic studies, animals are euthanized and gastrocnemius muscles, brain, heart and other organs are carefully dissected, weighed and subjected to DNA methylation studies. Additionally, the aforementioned model has been used by NASA as a common model to study simulated spaceflight induced weightlessness and cephalad fluid shift in animals is the hindlimb unloading model.
In summary, acute stress can affect our autonomic, endocrine and musculoskeletal performance (reviewed in [13]) as well as the gut microbiome dysbiosis that plays a significant role in regulating the behavior and health of its host [14]. The development of interventional strategies and/or reversal of pathophysiological effects in response to acute stress, requires a complete understanding of the underlying molecular mechanisms at the physiological and oral/gut microbiome level. A holistic approach using whole organisms involving metagenomics, metabolomics, metaproteomics and epigenetics is crucial to comprehend higher order processes as well as motor skills in response to acute stress. In this regard, the use of proposed model for has the potential to identify potential biomarkers involved in acute stress. If the agents identified are novel and the effects can be reversed, the outcomes may ultimately result in the development of new prebiotics, probiotics and postbiotics to improve human health. This will have a huge clinical impact worldwide, in diagnostic, therapeutics and/or risk prediction models. Overall, it is anticipated that the knowledge gained from such research has the potential to identify novel molecules that could be exploited for human health and performance, and it is a priority area of research.

Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.

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